Non-invasive characterization of chronic inflammatory bowel diseases (ulcerative colitis and Crohn´s disease) using 68Ga-FAPI PET/CT

Ziel/Aim: Inflammatory Bowel Disease (IBD), comprise a complex spectrum of chronic inflammatory conditions of the gastrointestinal tract (GIT) including ulcerative colitis (UC) and Crohn´s disease (CD). Management and monitoring of IBD necessitate the use of various diagnostic modalities including enteroscopy and cross-sectional imaging to assess disease activity, extent, and complications. Given the role of fibroblast activation and tissue remodeling in the pathophysiology of IBD, we aimed to explore the potential of the application of 68Ga-FAPI-PET in the context of IBD. Methodik/Methods: PET/CT (1 h post injection) with 68Gallium-labelled Fibroblast Activated Protein Inhibitors (68Ga-FAPI-PET/CT) were applied in 42 consecutive patients with pathologically confirmed IBD and a gender- and age-matched control group. Volumes of interest (VOIs) of standardized healthy GIT structures and visually FAPI-avid GIT-lesions were delineated using a isocontour tool. Uptake parameters (SUVmax and SUVmean) were analyzed with regard to differences between IBD entities and IBD disease activity status of patients (based on coloscopy findings and clinical parameters). FAP-expression in IBD tissue was evaluated by FAP-immunohistochemistry in biopsy samples. Ergebnisse/Results: 23 patients had UC and 19 CD. IBD patients showed significantly increased FAPI-uptake in most healthy appearing GIT structures compared to controls. FAPI-avid lesions of IBD patients showed overall high FAPI-uptake (SUVmax: 5.1 +/- 2.4, SUVmean: 2.9 +/- 1.3) CD lesions (n=31) showed slightly higher uptake than UC lesions (n=36) (CD: SUVmax/mean 5.7 +/- 2.8 / 3.1+/- 1.5 and UC: SUVmax/mean 4.6+/- 1.9 / 2.7+/- 1.0). Lesions of patients with active IBD showed markedly higher uptake (SUVmax/mean 5.3+/- 2.4 /3.0+/- 1.3). than lesions of patients with clinically inactive disease (SUVmax/mean 3.0+/- 0.9 / 2.0+/- 0.8). FAP-immunohistochemistry confirmed strong FAP-expression in chronic-inflammatory foci of CD and UC. Schlussfolgerungen/Conclusions: Our findings suggest high potential of 68Ga-FAPI-PET as a non-invasive imaging tool for assessing inflammatory activity in both UC and CD. Further research involving larger cohorts and standardized imaging protocols is warranted to validate the actual clinical value of FAPI-PET in IBD. Publication History Article published online: 12 March 2025 © 2025. Thieme. All rights reserved. Georg Thieme Verlag KG Oswald-Hesse-Straße 50, 70469 Stuttgart, Germany